1SEM_GETVALUE(3) Linux Programmer's Manual SEM_GETVALUE(3)
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6 sem_getvalue - get the value of a semaphore
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9 #include <semaphore.h>
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11 int sem_getvalue(sem_t *sem, int *sval);
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13 Link with -lrt or -pthread.
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16 sem_getvalue() places the current value of the semaphore pointed to sem
17 into the integer pointed to by sval.
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19 If one or more processes or threads are blocked waiting to lock the
20 semaphore with sem_wait(3), POSIX.1-2001 permits two possibilities for
21 the value returned in sval: either 0 is returned; or a negative number
22 whose absolute value is the count of the number of processes and
23 threads currently blocked in sem_wait(3). Linux adopts the former
24 behavior.
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27 sem_getvalue() returns 0 on success; on error, -1 is returned and errno
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31 EINVAL sem is not a valid semaphore.
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34 POSIX.1-2001.
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37 The value of the semaphore may already have changed by the time
38 sem_getvalue() returns.
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41 sem_post(3), sem_wait(3), sem_overview(7)
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44 This page is part of release 3.22 of the Linux man-pages project. A
45 description of the project, and information about reporting bugs, can
46 be found at http://www.kernel.org/doc/man-pages/.
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50Linux 2006-03-25 SEM_GETVALUE(3)